How Well Does Diadochokinetic Task Performance Predict Articulatory Imprecision? Differentiating Individuals with Parkinson's Disease from Control Subjects.

Objective: To investigate whether syllables produced in an oral diadochokinetic (DDK) task may be quantified so that persons with Parkinson's disease (PD) perceived to have reduced articulatory precision when reading may be correctly identified using that quantification.

Patients And Methods: Syllable sequences from 38 speakers with PD and 38 gender- and age-matched control speakers (normal controls [NC]) were quantified acoustically and evaluated in terms of (1) the speakers' ability to accurately predict speaker group membership (PD or NC) and (2) their ability to predict reduced/non-reduced articulatory precision.

Results: A balanced accuracy of 80-93% in predicting speaker group membership was achieved. The best measures were related to the proportion of a syllable made up of a vowel, amplitude slope and syllable-to-syllable variation in duration and amplitude. The best material was that based on /ka/. Reduced articulatory precision was accurately predicted from DDK measures in 89% of the samples. Release-transient prominence and voicing during the onset of plosives were particularly strong predictors.

Conclusions: DDK sequences can predict articulatory imprecision as observed in another speech task. The linking of performance across speech tasks probably requires measures of stability in syllable durations and amplitudes, as well as measures of subsyllabic acoustic features.